Can you please give your reference for that definitive statement. And what are 'nutritional studies'? Why wouldn't they include the research that led to the list of nutrient recommendations issued by USDA and similar publications in the UK, Norway, France, Australia and many other countries. No conclusions from them? I think there are. There is a truly vast literature on subjects nutritional so it's vital to be very specific.

Separately, when using the term 'ultraprocessed' we should be precise about the processes used. There are many different ones with undoubtedly different effects to different degrees on the nutrients therein.

The RDA and nutrient recommendations are the bare minimum so you do not die. Vast literature is ad populum fallacy.

Also consider that genetic background matters in nutritional matters and well... The populations under study have changed, and that's assuming you have a fairly similar background to a population and not very mixed.

And we are not even getting into how these things go down in practice, with heavy industry lobbying and what not...

TLDR, you are on your own in terms of optimal nutrition but as another commenter said "eat food, not too much, mostly plants"